Searles Lake evaporite sequences: Indicators of late Pleistocene/Holocene lake temperatures, brine evolution, and pCO2

Kristian J. Olson, Tim K. Lowenstein

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

Searles Lake, California, was a saline-alkaline lake that deposited >25 non-clastic minerals that record the history of lake chemistry and regional climate. Here, the mineralogy and petrography from the late Pleistocene/ Holocene (32–6 ka) portion of a new Searles Lake sediment core, SLAPP-SRLS17, is combined with thermodynamic models to determine the geochemical and paleoclimate conditions required to produce the observed mineral phases, sequences, and abundances. The models reveal that the primary precipitates formed by open system (i.e., fractional crystallization), whereas the early diagenetic salts formed by salinity-driven closed system back-reactions (i.e., equilibrium crystallization). For core SLAPP-SRLS17, the defining evaporite sequence trona → burkeite → halite indicates brine temperatures within a 20–29 °C range, implying thermally insulating lake depths >10 m during salt deposition. Evaporite phases reflect lake water pCO2 consistent with contemporaneous atmospheric values of ˜190–270 ppmv. However, anomalous layers of nahcolite and thenardite indicate pulses of pCO2 > 700–800 ppm, likely due to variable CO2 injection along faults.Core sedimentology indicates that Searles Lake was continuously perennial between 32 ka and 6 ka such that evaporite units reflect periods of net evaporation but never complete desiccation. Model simulations indicate that cycles of partial evaporation and dilution strongly influence long-term brine evolution by amassing certain species, particularly Cl–, that only occur in late-stage soluble salts. A model incorporating longterm brine dynamics corrects previous massbalance anomalies and shows that the late Pleistocene/Holocene (32–6 ka) salts are partially inherited from the solutes introduced into earlier lakes going back at least 150 ka

Original languageEnglish (US)
Pages (from-to)2319-2334
Number of pages16
JournalBulletin of the Geological Society of America
Volume133
Issue number11-12
DOIs
StatePublished - 2021

Bibliographical note

Funding Information:
The SLAPP-SRLS17 coring project would not be possible without the cooperation of Searles Valley Minerals Inc.; we give special thanks to Jade Brush. We thank our SLAPP-SRLS17 collaborators David McGee, Sarah Feakins, Joe Janick, Justin Stroup, Tripti Bhattacharya, Mark Peaple, Steve Lund, and Christine Chen for their valuable contributions and insights. Robert Demicco assisted with coding and provided suggestions that greatly improved an early draft of this manuscript. Logistical support during drilling and sample material used in this project provided by LacCore. This work was funded by the Comer Family Foundation and National Science Foundation Award 1903659, Paleo Perspectives on Climate Change Program, with additional support from the Geological Society of America, the American Association of Petroleum Geologists, and Society of Economic Geologists graduate student grants.

Funding Information:
The SLAPP-SRLS17 coring project would not be possible without the cooperation of Searles Valley Minerals Inc.; we give special thanks to Jade Brush. We thank our SLAPP-SRLS17 collaborators David McGee, Sarah Feakins, Joe Janick, Justin Stroup, Tripti Bhattacharya, Mark Peaple, Steve Lund, and Christine Chen for their valuable contributions and insights. Robert Demicco assisted with coding and provided suggestions that greatly improved an early draft of this manuscript. Logistical support during drilling and sample material used in this project provided by LacCore. This work was funded by the Comer Family Foundation and National Science Foundation Award 1903659, Paleo Perspectives on Climate Change Program, with additional support from the Geological Society of America, the American Association of Petroleum Geologists, and Society of Economic Geologists graduate student grants

Publisher Copyright:
© 2021 Geological Society of America

Continental Scientific Drilling Facility tags

  • SLAPP

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